Help! somethings wrong with my yellow TANG!!!!!

[Gnu-reefer]

hey guys, brand new here but a friend from msn told me you guys would be able to help me out. somethings wrong with my yellow tang, his fins are all torn and tattered... any ideas

some tank info,
29 gallon cube, running for 2 months,
salinity 1.025
Ammonia 0
Nitrite 0
Nitrate 5

any ideas?!?! hes looking worse and worse!!!!!!!!!!